After installing Avast! Computer doesn't boot

[1000Reasons]

Hi! I installed Avast! Antivirus yesterday, when the install finished it told me to restart computer. After restarting my computer it would just stay at the Apple logo and the loading wheel forever.. I have an iMac from 2009/2010. It has a AMD graphics card and a 4 core processor! I've tryed everything i've found abot the problem.. Still nothing has worked! I tryed:Resetting PRAM, removing all external devices, booting in safe mide, booting in repair mode, booting in single user mode, repaired harddrive, booted from harddrive manually and removing the power cable and holding the power button for 10 secs. Any help is very much appriciated..! Sorry for bad english!

 

[Kaveman]

Boot off the Recovery Partition and reinstall OSX to remove it.